• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 24
  • 9
  • 8
  • 4
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 51
  • 51
  • 13
  • 10
  • 9
  • 9
  • 9
  • 8
  • 8
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

The ecology of some British podzol formations

Dimbleby, G. W. January 1950 (has links)
No description available.
12

Influence of plexiglass inserts on prevention of root spiraling of container grown tree species

Agnew, Michael Lewis January 2011 (has links)
Typescript (photocopy). / Digitized by Kansas Correctional Industries
13

X-ray based tree ring analyses /

Lindeberg, Johan, January 2004 (has links) (PDF)
Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv. / Härtill 5 uppsatser.
14

Aspects of hybrid larch (Larix x eurolepis Henry) as a potential tree species in southern Swedish forestry /

Larsson-Stern, Marie, January 2003 (has links) (PDF)
Lic.-avh. (sammanfattning) Alnarp : Sveriges lantbruksuniv., 2003. / Härtill 3 uppsatser.
15

Híbridos de eucalipto sob diferentes regimes hídricos em vasos e crescimento no campo

Silva, Claudia Denise [UNESP] 22 February 2013 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:32:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-22Bitstream added on 2014-06-13T19:42:45Z : No. of bitstreams: 1 silva_cd_dr_jabo.pdf: 556845 bytes, checksum: 137ed59f1a755a580c83747ec967c0c8 (MD5) / O eucalipto apresenta crescimento rápido e boa adaptação às condições edafobioclimáticas brasileiras, constituindo-se na principal opção comercial para a oferta de madeira para diversos usos. Objetivou-se com este trabalho avaliar, em híbridos de Eucalyptus grandis x Eucalyptus urophylla, características de crescimento, fisiológicas e bioquímicas sob diferentes condições de disponibilidade hídrica e o crescimento inicial dos híbridos em campo. Foram avaliados cinco híbridos comerciais de eucalipto (H1, H2, H3, H4 e H5) em três experimentos diferentes. O primeiro experimento foi conduzido em vasos sob quatro condições de umidade do solo que foram determinados com base na capacidade máxima de retenção de água pelo substrato de forma a mantê-lo com 65%, 50%, 35% e 20% desta capacidade de retenção até o final do experimento, que durou 120 dias desde o plantio. Foram avaliadas nesse experimento as seguintes características de crescimento: altura, diâmetro do coleto, número de folhas, área foliar e massa seca de folhas, de caule + ramos, de raízes, da parte aérea e total e relação raiz/parte aérea; fisiológicas: taxas de fotossíntese líquida, condutância estomática, transpiração, número de estômatos, teor relativo de clorofila total, rendimento fotoquímico máximo do fotossistema II, eficiência de uso da água, eficiência instantânea da transpiração e potencial hídrico foliar e bioquímicas: quantificação de prolina e glicina. O segundo experimento, também em vasos, avaliou a sobrevivência dos cinco híbridos de eucalipto após a suspensão da irrigação. Além das características de crescimento e de trocas gasosas foi também computado o intervalo de tempo para a morte dos híbridos. Num terceiro experimento, os híbridos foram cultivados... / The eucalyptusgrows rapidly andadapts well to Brazilian edaphic andbioclimatic conditions. Itis the leading commercialoption for producing timber with a wide variety of uses. The objective of the research was toevaluate, in hybrids of Eucalyptus grandis x Eucalyptus urophylla, growth, physiologic and biochemical characteristics underdifferent conditions of availability of water and initial growth of hybrids in the field. Five commercial Eucalyptus hybrids(H1, H2, H3, H4 and H5) wereevaluated in three different experiments. The first one wasconducted inpots under foursoil moisture. The conditions were determinedbasedon the maximum capacityof water retention by substrate in order to keep it at65%, 50%, 35% and 20% of this capacity retention until the endof the experiment, whichlasted for 120 days since planting. In thisexperiment it was evaluatedgrowth characteristics asfollows:height, stemdiameter, number of leaves, leaf area anddryweight of leaves,stem + branches, roots, shootsand totalandrelation root / shoot in experimentsgreenhouse and height in the field experiment; physiological: ratesof net photosynthesis, stomatal conductance, transpiration,number of stomata, relative content of chlorophyll, maximum photochemical efficiency of photosystem II, efficienceof water use and leaf water potential; and biochemical: quantificationofprolineand glycine.Thesecond experiment, alsoconducted in pots evaluated the survival of five hybrids of eucalyptus after the suspension of irrigation. In addition the growth characteristics and gas exchange was also counted the range time for the death of hybrids. In the third experiment, the hybrids...(Complete abstract click electronic access below)
16

Híbridos de eucalipto sob diferentes regimes hídricos em vasos e crescimento no campo /

Silva, Claudia Denise. January 2013 (has links)
Orientador: Rinaldo Cesar de Paula / Banca: Mário Luiz Teixeira de Moraes / Banca: Luciana Duque Silva / Banca: Priscila Lupino Gratão / Banca: Sergio Valiengo Valeri / Resumo: O eucalipto apresenta crescimento rápido e boa adaptação às condições edafobioclimáticas brasileiras, constituindo-se na principal opção comercial para a oferta de madeira para diversos usos. Objetivou-se com este trabalho avaliar, em híbridos de Eucalyptus grandis x Eucalyptus urophylla, características de crescimento, fisiológicas e bioquímicas sob diferentes condições de disponibilidade hídrica e o crescimento inicial dos híbridos em campo. Foram avaliados cinco híbridos comerciais de eucalipto (H1, H2, H3, H4 e H5) em três experimentos diferentes. O primeiro experimento foi conduzido em vasos sob quatro condições de umidade do solo que foram determinados com base na capacidade máxima de retenção de água pelo substrato de forma a mantê-lo com 65%, 50%, 35% e 20% desta capacidade de retenção até o final do experimento, que durou 120 dias desde o plantio. Foram avaliadas nesse experimento as seguintes características de crescimento: altura, diâmetro do coleto, número de folhas, área foliar e massa seca de folhas, de caule + ramos, de raízes, da parte aérea e total e relação raiz/parte aérea; fisiológicas: taxas de fotossíntese líquida, condutância estomática, transpiração, número de estômatos, teor relativo de clorofila total, rendimento fotoquímico máximo do fotossistema II, eficiência de uso da água, eficiência instantânea da transpiração e potencial hídrico foliar e bioquímicas: quantificação de prolina e glicina. O segundo experimento, também em vasos, avaliou a sobrevivência dos cinco híbridos de eucalipto após a suspensão da irrigação. Além das características de crescimento e de trocas gasosas foi também computado o intervalo de tempo para a morte dos híbridos. Num terceiro experimento, os híbridos foram cultivados...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The eucalyptusgrows rapidly andadapts well to Brazilian edaphic andbioclimatic conditions. Itis the leading commercialoption for producing timber with a wide variety of uses. The objective of the research was toevaluate, in hybrids of Eucalyptus grandis x Eucalyptus urophylla, growth, physiologic and biochemical characteristics underdifferent conditions of availability of water and initial growth of hybrids in the field. Five commercial Eucalyptus hybrids(H1, H2, H3, H4 and H5) wereevaluated in three different experiments. The first one wasconducted inpots under foursoil moisture. The conditions were determinedbasedon the maximum capacityof water retention by substrate in order to keep it at65%, 50%, 35% and 20% of this capacity retention until the endof the experiment, whichlasted for 120 days since planting. In thisexperiment it was evaluatedgrowth characteristics asfollows:height, stemdiameter, number of leaves, leaf area anddryweight of leaves,stem + branches, roots, shootsand totalandrelation root / shoot in experimentsgreenhouse and height in the field experiment; physiological: ratesof net photosynthesis, stomatal conductance, transpiration,number of stomata, relative content of chlorophyll, maximum photochemical efficiency of photosystem II, efficienceof water use and leaf water potential; and biochemical: quantificationofprolineand glycine.Thesecond experiment, alsoconducted in pots evaluated the survival of five hybrids of eucalyptus after the suspension of irrigation. In addition the growth characteristics and gas exchange was also counted the range time for the death of hybrids. In the third experiment, the hybrids...(Complete abstract click electronic access below) / Doutor
17

Biomass and nutrient distribution in two old growth forest ecosystems in south coastal British Columbia

Krumlik, Jiri George January 1974 (has links)
The distribution of the above-ground biomass and macronutrient content of the trees were studied on two sample plots in south coastal British Columbia, near Vancouver. The plots differed in elevation (4,600 and 2,200 feet; 1,500 and 700 m), in soil type and depth. Tree age was similar in both plots, ranging from 150 to 530 years. The tree cover on the high elevation plot consisted of Tsuga mertensiana (Bong.) Carr. (mountain hemlock) and Abies amabilis (Dougl.) Forbes (Pacific silver fir) while the lower elevation plot was occupied by Tsuga heterophylla (Raf.) Sarg. (western hemlock), Thuja plicata D. Don (western red cedar) and Chamaecy- paris nootkatensis (D. Don) Spach (yellow cedar). Twenty-four trees were sampled to determine the biomass and nutrient content of wood, bark, branches, twigs, foliage and cones. Another nine trees were sampled for the biomass and nutrient content of wood and bark only. Multiple regression analysis was used to establish the relationship between d.b.h., tree length, crown length and biomass of the various tree components. The regression equations obtained were used to estimate the total biomass of wood, bark, branches, twigs and foliage contained in the trees on each of the sample plots. The data thus obtained were combined with data on chemical concentration and used to estimate the distribution of macronutrient elements in different above-ground biomass components of the stands. / Forestry, Faculty of / Graduate
18

Estimating the coefficients in a system of compatible growth and yield equations for Loblolly pine

Hans, Richard P. January 1986 (has links)
In this thesis the five equation system of growth and yield equations originally developed by Clutter (1963) is examined. The system is redeveloped algebraically to form a truly algebraically compatible system. Three methods of estimating the coefficients were examined. In the first method, three of the equations were fitted independently using ordinary least squares; these coefficient estimates were carried through to the other equations. No consideration was given to the relationships that must exist between the equation coefficients in order for the system to be numerically consistent. In the second method the system is first developed algebraically, before any of the coefficients are estimated, resulting in a slightly different system which is truly algebraically compatible. The coefficients were estimated by fitting two of the equations, and using these estimates throughout the rest of the system. The resulting system is both numerically consistent and algebraically compatible. In the final method the relationships between the coefficients that must hold for the system to be compatible were incorporated in the coefficient estimation procedure. Seemingly unrelated regression techniques were used to estimate the coefficients. The three methods resulted in coefficient estimates that were similar, with seemingly unrelated regression producing the most efficient estimators. Prediction ability of the three methods on independent data show no method as being superior, although the seemingly unrelated regression procedure was able to reduce the total system error best. / M.S.
19

Models of stand basal area distributions, individual tree basal area growth, and height-diameter relationships for loblolly pine

Green, Edwin James January 1981 (has links)
The study dealt with developing methodologies for predicting basal area distributions and individual tree basal areas. Data for the study was from the Hill Farm Experiment Station at Homer, Louisiana. Five height-diameter (basal area) curves were examined to determine which was most appropriate for the data set utilized. The model H = a + b log(BA), where H denotes height and BA denotes basal area, was chosen as best, based on several fit and prediction oriented statistics. A stochastic basal area distribution model, called the parameter distribution model, was developed. The model was based on the Chapman-Richards growth curve. This curve was fit to all stems on approximately 3/4 of the data set. Two parameters of the curve were fixed a priori, leaving two parameters to be estimated. A sampling distribution was fit to the estimates of the rate parameter, k. Models were developed to predict the parameters of this distribution from stand variables. A model was then derived to predict m, the shape parameter of the C-R curve, from k and stand variables. Finally, an existing survival function was modified. The overall model was implemented as follows: first, the number of surviving stems was predicted. Then k and m values were predicted for each predicted stem. Substitution of these two values into the C-R curve yielded a predicted basal area for each stem. The previously mentioned height diameter curve was employed to predict a height for each predicted basal area. Stochastic elements were built into the prediction model for m and the height-diameter curve. Predicted basal area and height distributions were compared to observed on the remaining 1/4 of the data set. Although the two--sample K-S test was statistically significant, the observed and predicted distributions did appear to be close, in general, from a practical standpoint. This approach appears promising as a stochastic method of predicting size distributions. The Chapman-Richards curve was also modified for use as an individual tree basal area growth model. Two parameters of the curve were fixed, and the remaining two were modelled as functions of tree- and stand-level variables. The modified growth function fit the data well, but on an independent data set, a simpler linear model of basal area growth performed better in terms of mean difference and mean absolute difference between observed and predicted basal areas. Thus, the only anticipated use of the modified C-R model is in situations where extrapolation beyond the range of observed data is required, since this model has desirable long-term characteristics, whereas the linear model does not. / Ph. D.
20

An integrated system of stand models for loblolly pine

Daniels, Richard F. January 1981 (has links)
An integrated system of stand models was developed for loblolly pine in which models of different levels of resolution are related by a unified mathematical structure. A “telescoping'' system is presented in which a highly detailed overall model is specified and its components. ''collapsed" around a common set of growth and survival functions to provide structurally compatible models at each successively lower stage of resolution. The most detailed model is a distance dependent individual tree model which simulates the growth and competitive interaction of trees in a stand. Tree basal area and height growth were modeled using a modified Chapman-Richards function in terms of potential growth, current size, relative size, crown ratio, and an index of competition. Potential growth was considered a function of site quality, age, and open-grown size relationships. Tree survival probability was described using a logistic function in terms of age, crown ratio, and competition. The competition or point density index is a function of the size and location of neighbors. Published indices were evaluated and compared on their simple correlation with growth, multiple correlation with growth in the presence of other tree and stand measures, computer execution time, and relationships to stand level density measures. The area potentially available (APA) for each tree was chosen as the most suitable. The APA index is calculated as the area of the polygon constructed from lines which divide the distance between a tree and its neighbors. Mean APA, or average area per tree, is estimated by the inverse of trees per unit area, permitting point density to collapse to stand density, resulting in a distance independent individual tree model. This model was collapsed dimensionally to consider trees grouped in size classes. Tree growth and survival equations are applied to the mean attributes of each size class, resulting in a size class projection model. At the lowest level of resolution, the dimensions of the model are collapsed to one "average" tree. A stand level projection model results from applying the tree growth and survival equations to the stand's average tree attributes. At the stand level, the basal area growth function provides a transformation which, for a number of probability density functions (pdf's), will regenerate the initial pdf family. Considering a normal pdf to describe basal area distributions, a pdf-based size distribution model is presented, in which the projected parameters are expressed in terms or the growth function coefficients. Applications to other pdf families are discussed. Preliminary tree growth and survival equation coefficients were estimated using data from a loblolly pine stand density study in North Louisiana. Structurally compatible models at each level of resolution are detailed. Considerations for numerically consistent estimates from models of different levels of resolution are discussed in terms of model specification, estimation, and implementation. Recommendations for model application and future model development are presented. / Ph. D.

Page generated in 0.0302 seconds